JPWO2009054319A1 - Load control device and lighting device - Google Patents

Abstract

A discharge lamp lighting device capable of accurately controlling a load while improving practicality is provided. The prediction circuit 35 predicts the timing at which the current value iQ1 reaches the peak value based on the change rate of the difference in the state where the difference of the count number Nn is equal to or less than the predetermined threshold value. The switch selection circuit 38 driven at a clock frequency higher than the sampling frequency of the first converter 32 turns off the field effect transistor Q1 and turns on the field effect transistor Q2 at the turn-off timing. A plurality of A / D converters 37a are multi-rate controlled to correct the threshold value of the prediction circuit 35 based on the peak value of the lamp current iout. Even if the peak values of the current values iQ1 and iQ2 are located during the sampling period of the first converter 32, the turn-off timing can be accurately set according to the current values iQ1 and iQ2 without increasing the sampling frequency more than necessary. Therefore, practicality is improved and the lighting of the fluorescent lamp can be controlled accurately.

Description

  The present invention relates to a load control device having an inverter circuit including a switching element for driving a load, and an illumination device including the load control device.

Conventionally, as this type of load control device, an inverter unit that converts a DC power source into an AC power source, a discharge lamp that is lit and driven by the inverter unit, and a detection unit that detects a current value and a voltage value of the discharge lamp, respectively A / D converter for A / D converting analog current values and voltage values of the detected discharge lamp, and a reference value for controlling the inverter unit according to the digital quantity detected by the A / D converter There is known a discharge lamp lighting device that includes a calculation unit that calculates the above and a control unit that controls the inverter unit based on a reference value calculated by the calculation unit (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-41079 (page 3-4, FIG. 1)

  However, for example, an 8-bit A / D converter usually has a sampling frequency of about 1 MHz to 2 MHz and has a resolution of about 0.5 μs to 1.0 μs. Therefore, in the above-described discharge lamp lighting device, The current value or voltage value of the switching element cannot be sampled sufficiently.

  Therefore, although the operation of the inverter unit is controlled based on the average value of each sampling value, it is not easy to accurately control the inverter unit with such control.

  On the other hand, although it is possible to improve the resolution by using an A / D converter having a sampling frequency sufficiently higher than the switching cycle, or to perform multi-rate control using a plurality of A / D converters, In such a case, there is a problem that current consumption increases or becomes expensive, which is not practical.

  The present invention has been made in view of these points, and an object of the present invention is to provide a load control device capable of accurately controlling a load while improving practicality, and an illumination device including the load control device.

  The load control device according to claim 1 is an inverter circuit including a switching element for driving a load; and converts an analog current value flowing through the switching element in an ON state into a digital quantity corresponding to the current value at a predetermined sampling frequency. The difference between the digital quantity converted at a predetermined timing by the first conversion means and the digital quantity at the next timing of the timing is equal to or less than a predetermined threshold value. Predicting means for predicting the timing at which the current value flowing through the switching element reaches a peak value based on the rate of change; driven at a clock frequency higher than the sampling frequency of the first converting means and in the on state at the timing predicted by the predicting means The switching element is turned off and the switching element in the off state is turned on. Control means for turning on; second conversion means for converting the electric quantity output from the load into a digital quantity; detecting a peak value of the electric quantity output from the load by the digital quantity converted by the second conversion means; Correction means for correcting the timing prediction of the prediction means based on this detection.

  As the inverter circuit, for example, an inverter circuit of a half bridge type or a full bridge type is used.

  As the first conversion means, for example, a voltage controlled oscillator having an oscillation frequency of about 50 MHz or an 8-bit flash type A / D converter is used.

  As the prediction means, for example, a DSP (Digital Signal Processor) is used.

  For example, a DSP or the like is used as the control unit, and the control unit may be provided integrally with the prediction unit, or may be separate from the prediction unit.

  As the second conversion means, for example, a plurality of A / D converters or voltage controlled oscillators are used, and the amount of electricity output from the load is larger than each sampling frequency by performing multi-rate control of these. It can be converted to a digital quantity at the sampling frequency.

  For example, a DSP or the like is used as the correction unit, and the correction unit may be provided integrally with the prediction unit or the control unit, or may be separate from the prediction unit and the control unit.

  Then, in a state where the difference between the digital quantity converted at a predetermined timing by the first conversion means and the digital quantity at the next timing is equal to or less than a predetermined threshold value, a prediction is made based on the change rate of the difference. The timing at which the current value flowing through the switching element reaches the peak value is predicted by the means, and the control means driven at a clock frequency higher than the sampling frequency of the first conversion means is turned on at the turn-off timing predicted by the prediction means. The switching element is turned off, the switching element in the off state is turned on, and the amount of electricity output from the load is converted into a digital amount by the second conversion means, and the peak of the amount of electricity output from the load is converted by this digital amount. The variable setting means detects the value of the prediction means based on the detection. The switching element is corrected even if the peak value of the current flowing through the switching element is located during the sampling period of the first converter without increasing the sampling frequency of the first converter more than necessary by correcting the prediction of Since the turn-off timing is accurately set according to the current value, the practicality is improved and the load can be controlled accurately.

  The load control device according to claim 2 is the load control device according to claim 1, wherein the prediction means has a peak value of a current value flowing through the switching element based on an absolute amount of the digital quantity converted by the first conversion means. The timing is predicted, and the control unit turns off the switching element in the on state and turns on the switching element in the off state at the timing predicted by the prediction unit.

  Then, based on the absolute value of the digital quantity converted by the first conversion means, the prediction means predicts the timing at which the current value flowing through the switching element reaches the peak value, and the switching means in which the control means is in the ON state at the predicted timing. Is turned off, and the switching element in the off state is turned on, so that the peak value of the current value of the switching element can also be determined based on the absolute value of the digital quantity as well as the change rate of the difference of the digital quantity converted from the current value flowing through the switching element. The switching element can be turned off according to the value, and the load can be controlled more accurately.

  A load control device according to a third aspect is the load control device according to the first or second aspect, wherein the control means turns off the switching element when the rate of change of the difference in the prediction means increases.

  When the rate of change of the difference in the predicting means increases, the control means turns off the switching element, thereby preventing an overcurrent due to a circuit abnormality or the like.

  A lighting device according to a fourth aspect includes the load control device according to any one of the first to third aspects; and an appliance main body to which a discharge lamp as a load that is turned on by the load control device is attached. It is.

  And each effect | action is show | played by providing the load control apparatus as described in any one of Claim 1 thru | or 3.

  According to the load control device of the first aspect, the difference between the digital quantity converted at the predetermined timing by the first conversion means and the digital quantity at the timing next to the timing is not more than the predetermined threshold value. Based on the rate of change of the difference, a clock having a frequency higher than the sampling frequency of the first conversion unit is generated by the prediction unit to predict the turn-off timing of the switching element between the sampling timings of the first conversion unit. At the turn-off timing, the control means turns off the switching element in the on state, turns on the switching element in the off state, and converts the amount of electricity output from the load into a digital quantity by the second conversion means. The peak value of the electric quantity output from the load is detected by the digital quantity. Based on this detection, the variable setting means corrects the timing prediction of the prediction means, so that the turn-off timing can be accurately determined according to the current value of the switching element without increasing the sampling frequency of the first conversion means more than necessary. Since it can be set, the utility can be improved and the load can be controlled accurately.

  According to the load control device according to claim 2, in addition to the effect of the load control device according to claim 1, the current value at which the prediction means flows through the switching element based on the absolute amount of the digital quantity converted by the first conversion means. Is the digital value obtained by converting the value of the current flowing through the switching element by predicting the timing at which the peak value is reached and turning off the switching element in the on state and turning on the switching element in the off state at the predicted timing. The switching element can be turned off in correspondence with the peak value of the current value of the switching element, based on the absolute value of the digital quantity as well as the change rate of the difference in quantity, and load control can be performed more accurately.

  According to the load control device of the third aspect, in addition to the effect of the load control device according to the first or second aspect, when the rate of change of the difference in the prediction means increases, the control means turns off the switching element. By doing so, it is possible to prevent overcurrent caused by circuit abnormality.

  According to the illumination device of the fourth aspect, the load control device according to any one of the first to third aspects is provided, so that each effect is exhibited.

It is a block diagram of a part of a load control device showing an embodiment of the present invention. It is a circuit diagram of a load control apparatus same as the above. It is a perspective view which shows the external appearance of the illuminating device provided with the load control apparatus same as the above. It is a graph which shows the load of a load control apparatus same as the above, and the electric quantity of each switching element. It is explanatory drawing which shows operation | movement of the 1st conversion means of a load control apparatus same as the above. It is explanatory drawing which shows each detection algorithm of the peak value of the electric current value of the switching element of a load control apparatus same as the above, and the peak value of the electric quantity of load. It is explanatory drawing which expands and shows a part of detection algorithm of the peak value of the electric current value of the switching element of a load control apparatus same as the above.

Explanation of symbols

11 Lighting equipment
12 Instrument body
16 Discharge lamp lighting device as load control device
22 Inverter circuit
32 1st conversion part as 1st conversion means
35 Turn-off prediction circuit having functions of prediction means and correction means
37a A / D converter as second conversion means
38 Switch selection circuit as control means
Fluorescent lamp that is a discharge lamp as FL load
Q1, Q2 Field effect transistors as switching elements

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 is a block diagram of a part of the load control device, FIG. 2 is a circuit diagram of the load control device, FIG. 3 is a perspective view showing an appearance of a lighting device including the load control device, and FIG. FIG. 5 is an explanatory diagram showing the operation of the first conversion means of the load control device, and FIG. 6 is a peak value of the current value of the switching device of the load control device and a peak of the load electric amount. FIG. 7 is an explanatory diagram showing an enlarged part of a detection algorithm for the peak value of the current value of the switching element of the load control device.

  As shown in FIG. 3, reference numeral 11 denotes an illuminating device, and the illuminating device 11 has an instrument body 12, and a reflecting surface 13 is formed on the lower surface of the instrument body 12, and the reflecting surface 13 is arranged in the longitudinal direction. Lamp sockets 14 and 14 are mounted at both ends, and between these lamp sockets 14 and 14, a straight tube type fluorescent lamp FL which is a discharge lamp as a load is electrically and mechanically attached. Further, a discharge lamp lighting device 16 as a load control device shown in FIG.

As shown in FIG. 2, an inverter circuit 22 as a discharge lamp lighting circuit is connected to a DC power source 21 rectified and smoothed from a commercial AC power source (not shown). This inverter circuit 22 is a field effect transistor (FET) Q1 as a switching element. And a half-bridge type in which the field effect transistor Q2 is connected in series, and an inverter current i _out0 (FIG. 4B) flows.

  Further, a digital control circuit 23, which is a digital control unit as a control circuit, is connected to the gates of these field effect transistors Q1 and Q2.

  The connection point of the field effect transistor Q1 and the field effect transistor Q2 is connected to one end side of the fluorescent lamp FL via a series circuit of a DC cut capacitor C1 and an inductor L, and the other not shown of the fluorescent lamp FL The side is connected to the negative electrode of the DC power supply unit 21. Further, a starting capacitor C2 is connected in parallel to the fluorescent lamp FL.

As shown in FIG. 1, the digital control circuit 23 selects the current values i _Q1 and i _Q2 (FIG. 4 (c) and FIG. 4 (d)) flowing in the field effect transistors Q1 and Q2, respectively. 31 is connected to a first conversion unit 32 as a first conversion unit, a zero-cross detection circuit 33, and a synchronization signal generation circuit 34. The first conversion unit 32 includes a prediction unit and a correction unit, respectively. The turn-off prediction circuit 35 (hereinafter referred to as the prediction circuit 35) having the following functions is connected to the prediction circuit 35. The rectifier circuit 36 and the second conversion unit 37 are connected to the prediction circuit 35, and the selection circuit 31 and the prediction circuit 35 Are connected to a switch selection circuit 38 as control means. Hereinafter, at least one or both of the current values i _Q1 and i _Q2 may be simply referred to as a current value i.

  The selection circuit 31 detects and selects one of the field effect transistors Q1 and Q2 in which the current flows, and outputs the current value to the first conversion unit 32. Note that the selection circuit 31 may be configured to forcibly select one of the field effect transistors Q1 and Q2.

  The first conversion unit 32 is configured by sequentially connecting, for example, a current control oscillator (ICO) 41 as an A / D conversion unit and a counter 42 as a measuring unit.

  When the current value i selected by the selection circuit 31 is input, the current control oscillator 41 samples the current value i at a predetermined sampling frequency that is the sampling period of the first converter 32, for example, a frequency of 50 MHz ( 5 (a) and 5 (b)), a clock signal f having a frequency corresponding to the current value i is output as a digital quantity corresponding to the sampled current value i. For example, the current control oscillator 41 outputs a clock signal f having a large frequency when the current value is large. Instead of the current control oscillator 41, a current / voltage converting means for converting the current value i into a voltage value, and the voltage value converted by the current / voltage converting means is sampled at a predetermined sampling frequency to obtain the clock signal f. An output voltage controlled oscillator (VCO) may be used.

The counter 42 counts the clock signal f output from the current control oscillator 41 for a predetermined time. The count number of the clock signal f counted by the counter 42 is, for example, when the switching period of the field effect transistors Q1 and Q2 is 10 μs (switching frequency 100 kHz) and the sampling frequency of the current control oscillator 41 is 50 MHz. When the time width T _samp1, which is the sampling period in the circuit 34, is 0.1 μs (sampling frequency 10 MHz), for example, about five, and when the time width T _samp1 is 0.2 μs (sampling frequency 5 MHz), for example, about ten time widths For example, when T _samp1 is _{0.5 μs} (sampling frequency 2 MHz), about 25, and when the time width T _samp1 is _{1.0 μs} (sampling frequency 1 MHz), about 50 can be taken. Then, the counter 42 outputs the count number N _n obtained by taking the average value for each time width T _{samp1, n} to the prediction circuit 35.

The zero-cross detection circuit 33 detects a zero-cross point (a point where the current value i changes from negative to positive) and outputs the detection timing to the synchronization signal generation circuit 34. The output is generated from the synchronization signal generation circuit 34 by this output. The timing of starting each of the current control oscillator 41 and the counter 42 is reset by the synchronization signal for each time width T _samp1 , and the sampling period of the first conversion unit 32 can be synchronized with the zero cross point of the current value i. ing. In other words, the sampling period of the first converter 32 is synchronized with the switching period of the inverter circuit 22 (FIG. 2). Note that the sampling period of the first converter 32 does not have to be synchronized with the switching period of the inverter circuit 22 (FIG. 2). In this case, the zero-cross detection circuit 33 may not be provided.

The prediction circuit 35 has a difference N _D = N _n −N _n between the count number N _n , which is a digital quantity converted at a predetermined timing by the first conversion unit 32, and the count number N _n of the next timing after that timing. _-1 is less than or equal to a predetermined threshold value N _DREF , the rate of change of this difference N _D , that is, N _{DD, n} = N _{D, n} −N _{D, n−1} , N _{DD, n−1} = N _{D, n-1} -ND _{, n-2} ..., N _{DD, nv} = N _{D, nv -Based on the} rate of change of _{Nd, nv-1} , the current value i _{Q1 of the} field effect transistors Q1, Q2 or The timing at which any of the current values _iQ2 reaches the peak value can be predicted (FIG. 6 (a) and FIG. 6 (b)). Further, the prediction circuit 35 calculates the absolute value of the digital quantity in each time width T _{samp1, k} (k = 1, 2,..., N−1, n,...), That is, each count number N _k (k = .., N−1, n,...), The timing at which either the current value i _Q1 or the current value i _Q2 becomes a peak value can be predicted.

The rectifier circuit 36 performs full-wave rectification on the amount of electricity of the fluorescent lamp FL, for example, an AC lamp current i _out (FIG. 4A), which is an output current, and outputs it to the second converter 37. The amount of electricity of the fluorescent lamp FL may be, for example, an output voltage or power.

The second conversion unit 37 includes a plurality of A / D converters 37a serving as second conversion means, and the A / D converters 37a are operated by multi-rate control, that is, by shifting the phases by a predetermined amount. The lamp current i _out of the fluorescent lamp FL output from the rectifier circuit 36 is A / D converted into a digital quantity (FIG. 6 (c)). Therefore, the second conversion unit 37 has a sampling frequency larger than the sampling frequency of each A / D converter 37a, that is, a time width T _samp2 smaller than the sampling time width of each A / D converter 37a. Sampling data. The second conversion unit 37 is instructed by the prediction circuit 35 for sampling timing.

  As the second conversion unit 37, as long as comparison with an analog reference amount or temperature correction is possible, the voltage conversion oscillator similar to the first conversion unit 32 is used instead of each A / D converter 37a. And a plurality of counters may be provided, or a single A / D converter 37a may be used.

  The switch selection circuit 38 is connected to the gates of the field effect transistors Q1 and Q2, and controls the switching of the field effect transistors Q1 and Q2 at the timing predicted by the prediction circuit 35. The switch selection circuit 38 normally switches the field effect transistors Q1 and Q2 at a switching frequency of about 100 kHz (switching cycle of about 10 μs).

  Next, the operation of the above embodiment will be described.

  The high-frequency voltage output from the inverter circuit 22 by switching the field effect transistors Q1 and Q2 by the digital control circuit 23 is converted into a resonance voltage by resonance of the DC cut capacitor C1, the inductor L, and the start capacitor C2. This resonance voltage preheats the filament of the fluorescent lamp FL and is applied between the filaments to light the fluorescent lamp FL.

Here, in the digital control circuit 23, when the zero cross detection circuit 33 detects one of the current values i _Q1 and i _Q2 , for example, the timing at which the current value i _Q1 changes from negative to positive, this zero cross detection signal is selected as a selection circuit. 31, the selection circuit 31 selects the current value i _Q1, and the selected current value i _Q1 is converted into a clock signal f having a frequency corresponding to the absolute amount by the current control oscillator 41 of the first converter 32. At the same time, the converted clock signal f is counted by the counter 42.

  At this time, since the zero cross detection signal from the zero cross detection circuit 33 is also input to the synchronization signal generation circuit 34, the operation timing of the current control oscillator 41 and the counter 42 is reset, and the current control oscillator 41 (first conversion) The sampling period of the unit 32) is synchronized with the switching period of the inverter circuit 22.

Next, when the counter 42 _inputs the count number N _{n in} each time width T _{samp1, n} (n = 1, 2,...) To the prediction circuit 35, the prediction circuit 35 _{sets the} count number N _n to this count number N _n . Based on this, the difference N _{D, n} is calculated. Then, the turn-off timing T _{to, u} of the field effect transistor Q1 is predicted in a state where the difference N _{D, n} is equal to or less than a predetermined threshold value N _DREF , that is, N _{D, n} ≦ N _DREF .

Specifically, the prediction circuit 35, the difference N _DD, i.e. _{N DD, n = N D,} n -N D, n-1, N DD, n-1 = N D, n-1 -N D, n- ₂ ..., N _{DD, nv-1} = N _{D, nv} -N _{D, nv-1} is calculated, and a clock frequency higher than the sampling frequency of the first converter 32 is generated based on the rate of change. is allowed, a small time width _T-to than the time width T _SAMP1, the time width T _{samp1, n + k (k} is an arbitrary natural number of 1 or more), i.e. located in the time width T _SAMP1 after the k sampling periods The timing of the peak value of the current value i _Q1 is predicted (FIG. 7). Here, when the change rate of the difference N _DD becomes smaller, it is determined that the peak value is approaching, and when the change rate of the difference N _DD is equal to or less than a predetermined value, it is determined that the peak value is reached. Although k is normally set to 1 or 2, for example, _when the setting resolution of the threshold value N _DREF is insufficient, this lack of setting resolution can be compensated by increasing k.

In addition, for example, when the timing T _{to, u} is predicted in a region where the slope of the current flowing through the field effect transistor Q1 does not change, the switching frequency of the field effect transistors Q1, Q2 changes significantly to set the timing T _{to, u} . In a state where the prediction cannot be properly performed, the prediction circuit 35 predicts the timing T _{to, u} as the timing at which the current value i _Q1 reaches the peak value based on the absolute amounts of the plurality of count numbers N _n . The target peak value of the current value i is set by the difference between the lamp current i _out and the target value.

Then, according to the timing T _{to, u} predicted by the prediction circuit 35, the prediction circuit 35 controls the switch selection circuit 38 with a minute width PWM signal having a time width T _to. The field effect transistor having the value i selected, in this embodiment, the field effect transistor Q1 is turned off at the timing T _{to, u} predicted by the prediction circuit 35, and the field effect transistor Q2 is turned on at the timing T1 or T2.

On the other hand, the lamp current i _out is rectified by the rectifier circuit 36, and each A / D converter 37a of the second converter 37 is multi-rate controlled, and after a delay of time τ _D1 from the timing T _{to, u Is} converted into a digital quantity with a time width T _samp2 .

The prediction circuit 35 detects the peak value of the lamp current i _out based on the converted digital quantity, and corrects the threshold value N _DREF as appropriate based on this detection.

At this time, as the digital quantity of the second conversion unit 37 used for correcting the threshold value N _DREF , for example, when the time width T _samp2 is relatively short, the average value of the digital quantities converted by the A / D converters 37a is used. When the time width T _samp2 is relatively long, the maximum value or the minimum value of the digital amount converted by each A / D converter 37a is used.

As a result, at the corrected timing, that is, at the timing delayed by time τ _D2 from the detection timing of the peak value of the lamp current i _out , the field effect transistor Q2 is turned off similarly to the turn-off control of the field effect transistor Q1, and the electric field The effect transistor Q1 is turned on. In other words, the turn-off timing (PWM signal output) after a half cycle of the switching cycle of the field effect transistors Q1 and Q2 is corrected.

  Thereafter, the control is repeated alternately for the field effect transistors Q1 and Q2.

As described above, in a state where the difference N _{D, n} between the count number N _n−1 converted by the first conversion unit 32 and the next count number N _n is equal to or less than a predetermined threshold value N _DREF , based on the rate of change of the difference N _D, the current value i _Q1 flowing through the field effect transistors Q1, Q2 by the prediction circuit 35, i _Q2 timing _T-to as a peak _value, to predict _u, timing T of the predicted off _{To, u} , the switch selection circuit 38 is turned on, and in this embodiment, the field effect transistor Q1 is turned off, and the field effect transistor in the off state, in this embodiment, the field effect transistor Q2 is turned on. and converts the timing _T-to turn-off predicted by prediction circuit _35, and multi-rate control a plurality of a / D converters 37a in the vicinity of _u the lamp current i _out into digital amount, which Digital quantity by detecting the peak value of the lamp current i _out, corrects the prediction of timing for prediction circuit 35 on the basis of this detection, in particular by correcting the threshold value N _DREF, the sampling frequency of the first converter 32 Even if the peak value of the current value i is located during the sampling period of the first conversion unit 32, the turn-off timing T _{to, u} is accurately set according to the current value i. As a result, practicality improves and lighting control of the fluorescent lamp FL can be accurately performed.

Further, the prediction circuit 35 predicts the timing at which the current value i reaches the peak value based on the absolute amount of the count number N _n converted by the first conversion unit 32, and the switch selection circuit 38 is turned on at the predicted timing. field effect transistor of the state, the turning off the field effect transistor Q1 here, field effect transistors in the oFF state, wherein by turning on the field effect transistor Q2, along with the rate of change of the difference n _D of the count number n _n, current Even based on the absolute value of the value i, the field effect transistor, here, the field effect transistor Q1 can be turned off in correspondence with the peak value of the current value i, and load control can be performed more accurately.

Further, the timing _T-to the current value i reaches a peak value by calculation results, such as the difference N _D of several periods before the count number N _n of T _SAMP1 as the peak _value, the calculated predict _u, the computation time It can be secured.

Since the turn-off timing is set by the current values i _Q1 and i _Q2 of the field effect transistors Q1 and Q2 close to the input side of the discharge lamp lighting device 16, the responsiveness is good. In particular, in the lighting device 11, if the response is slow, the fluorescent lamp FL may disappear or flicker. Therefore, it is possible to reliably prevent such disappearance or flicker by improving the response.

Also, when the rate of change of the difference N _D in the prediction circuit 35 in the normal case the decreasing is increased, when the switch selection circuit 38 turns off the field effect transistor Q1 or field effect transistor Q2, a field-effect transistor It can prevent overcurrent due to circuit abnormality due to abnormality of Q1 and Q2.

In the above-described embodiment, it is possible to control only one of the field effect transistors Q1 and Q2 to control the lamp current i _out for each cycle. In this case, the field effect transistor Q2 side is preferable because it is easier to control.

  Further, the setting of the turn-off timing may be controlled to be performed every cycle during the transition period of the discharge lamp lighting device 11, and to be performed every several cycles during the stable period.

  Further, the first conversion unit 32 may be, for example, an 8-bit flash type A / D converter having the same functions as the current control oscillator 41 and the counter 42. In this case, for example, it may be shared with any one of the A / D converters 37a of the second conversion unit 37.

As the amount of electricity of the load, other than the output current such as the lamp current i _out , for example, the output voltage and power can be similarly controlled.

Further, the correction means may be controlled so as to change the value of k of the time width T _{samp1, n + k} , or may be used in combination, instead of correcting the threshold value N _DREF .

  The load control device can also be used for loads other than the fluorescent lamp FL.

  The present invention is used in, for example, a home lighting device.

Claims (4)

An inverter circuit having a switching element for driving a load;
First conversion means for converting an analog current value flowing through the switching element in the ON state into a digital quantity corresponding to the current value at a predetermined sampling frequency;
In a state where the difference between the digital amount converted at a predetermined timing by the first conversion means and the digital amount at the next timing is equal to or less than a predetermined threshold, the switching element is set based on the change rate of the difference. A predicting means for predicting the timing when the flowing current value reaches the peak value;
A control unit that is driven at a clock frequency higher than the sampling frequency of the first conversion unit and turns off the switching element in the on state and turns on the switching element in the off state at a timing predicted by the prediction unit;
Second conversion means for converting an electrical quantity output from a load into a digital quantity;
Correction means for detecting the peak value of the electric quantity output from the load from the digital quantity converted by the second conversion means and correcting the prediction of the timing of the prediction means based on this detection;
A load control device comprising: The predicting means predicts the timing at which the current value flowing through the switching element becomes a peak value based on the absolute amount of the digital quantity converted by the first converting means,
The load control device according to claim 1, wherein the control means turns off the switching element in the on state and turns on the switching element in the off state at the timing predicted by the prediction means. The load control device according to claim 1 or 2, wherein the control means turns off the switching element when the rate of change of the difference in the prediction means increases. A load control device according to any one of claims 1 to 3;
An appliance main body to which a discharge lamp as a load to be lit by the load control device is attached;
An illumination device comprising:

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